This invention relates to method of making lithium borohydride that gives high yield and allows easier purification than previous methods.
Another method of making lithium borohydride, as disclosed by H. C. Brown, et. al. in Inorganic Chemistry, vol. 21, pp. 3657–3661, 1982 (herein called “Brown, et. al.”), involves reacting sodium borohydride with lithium chloride in the presence of a solvent, with glass beads of 6 millimeter diameter present in the reaction container. Brown et. al. teach that, to produce a batch of lithium borohydride larger than 2.2 grams, the use of glass beads or other small solid inert objects called “attrition media” is necessary to achieve yields that are large enough to be useful.
Attrition media are known in the chemical arts and are described, for example, in Perry's Chemical Engineer's Handbook, 7th edition, 1997, “Crushing and Grinding Equipment” (herein called “Perry”). As taught by Perry, attrition media are chosen to be inert to the chemical process in which they are used; some typical materials are sand, glass, and steel. Perry further teaches that attrition media are typically spherical, cylindrical, or irregular in shape, and they typically range in size from 0.2 to 15 millimeters. According to the teaching of Perry, attrition media are often used for the purpose of breaking down the particles of some powdered material; in such cases, the size of the attrition media is typically chosen to be 10 to 100 times larger than the particles of the powdered material.
In the production of lithium borohydride, the presence of glass beads or other similar attrition media in the reaction container would create severe complications in the manufacturing process. The beads take up volume in the reaction container, reducing the productivity of the reactor. The beads add difficulty to removing the lithium borohydride from the reaction vessel, and they add difficulty to isolating the byproducts for disposal. The problem addressed by this invention is the provision of a method of making lithium borohydride in high yield, in a good solvent, without the need for glass beads or other attrition media.